you wouldn't necessarily have to regear, but it would be sluggish on the highway without the regear.

and no the tires would not rub if you have a 4 to 3.5 inch backspacing. i ran 33x12.50s with on my 3.25 backspacing (sticks the tire farther out than a 4 inch, opposite of what you'd think) at stock height with hardly any rubbing at all